Sediments and benthos of northeastern Great Barrier Island, New Zealand

Abstract

We studied the sediments and benthos in 24 dredge samples taken from a 20 km 2 area of sea bed (3–60 m depth) along the northeastern coast of Great Barrier Island, northeast New Zealand, These results extend an earlier study of 10 km 2 of adjacent sea floor. Five benthos associations and one subassoeiation are recognised and mapped. A polychaete-crustacean association, characterised by attached or encrusting forms and a mobile epifauna, lives in coarse sand and pebble gravel in a number of areas shallower than 50 m , Gravel patches at around 45 m depth are probably relict beach gravels formed ca. 12,000 years ago, Two infaunal bivalve associations occur in 1–28 m depth of water: Myadora-Scalpomactra in fine to medium sand beneath moderately turbid water; Gari-Felaniella mostly in pebbly medium to coarse sand beneath clearer water. An association dominated by the sand-dwelling bryozoan Otionella covers a large area of fine to coarse sand at 25–55 m depth, An Otionella-Zeacolpus subassoeiation occurs in several places around the shallow margins of the Otionella association. An infaunal bivalve — ophiuroid association, Cuspidaria-Amphiura-Notocallista, lives in slightly muddy to muddy fine sand over a large area between 40 and 70 m + depth